In general, examples of a coated sheet include various optical functional films having an optically functional layer. Formerly, the main currents of displays of OA instruments, such as TVs and desktop personal computers, were CRTs. However, the main currents have been changed to liquid crystal displays, which have great advantages such as thinness and lightness, and low power consumption. Liquid crystal displays spreading at present have optically functional layers such as a liquid crystal layer for forming a phase difference film, a hard coat layer for surface-protection, and an antireflective layer.
In order to yield such an optically functional layer, methods of applying an optically functional layer onto a substrate film have been variously used hitherto. Various coated sheets wherein a coating layer is formed by conducting the application of a coating solution onto a substrate film, drying it, and subjecting to some other steps are produced (see, for example, Japanese Patent Application Laid-Open No. 62-140672). General examples of the coating method for a thin layer include a slot die coater and a gravure coater.
In recent years, with enhancement in the performance of optical functions, it has been becoming essential to improve the evenness of a coating film which gives the function. Thus, it has been becoming important to not only select the coating method but also control the drying step after coating (see, for example, Japanese Patent Application Laid-Open No. 8-94836).
However, even if any coating method is used, resin-flow is caused during the shift from the coating step to the drying step. Thus, it is difficult to form a coating layer having an even film thickness. It is particularly difficult to form a coating layer having an even film thickness onto a substrate film having a large area.
For example, in the case that a hard coat layer, an antireflective layer and so on are formed on a polymer film, laminated layers have different refractive indexes. Consequently, a particularly serious problem is interference unevenness, which results from thickness unevenness generated by the flow of the resins after the application of the coating solutions. In this case, the in-plane optical thickness becomes uneven so that the reflectivity characteristic becomes lower than the theoretical value.
It is known that in general liquid crystal molecules which constitute a liquid crystal layer are very easily affected by the interface thereof so that the liquid crystal molecules are arranged (oriented) to have aromaticity by surface-regulating force such as rubbing. In the case of the above-mentioned coating methods, a single surface of the applied coating solution containing liquid crystal molecules becomes an open system; consequently, according to ordinarily-known coating and drying methods, the flow of the air on the open system side causes orientation unevenness of the liquid crystal layer. The thus-obtained liquid crystal layer causes a problem that the front face contrast of the liquid crystal display changes partially.